Multiple Pipeline JSONNET flatten array throwing error

I am using [ std.flattenArrays( [ ArrayofPipelineA, ArrayOfPipelineB ] ) ]
in my .drone.jsonnet file. If I run this file in DroneCI it throws error “yaml: unmarshal errors: line 1: cannot unmarshal !!seq into yaml.RawResource”. But if I convert the same file with the below command(keeping the original with .bak and creating new file)

jsonnet -y .drone.jsonnet.bak > .drone.jsonnet

it works perfectly in DroneCI.
I assume multiple pipeline is not the error here since the converted file works perfectly.

What can be the probable error?

Hey I made a mistake on nesting array, it was solved by only writing std.flattenArrays( [ ArrayofPipelineA, ArrayOfPipelineB ] )